Invasive plants pose a serious threat to native ecosystems by altering the composition of plant communities, reducing biodiversity, changing soil structure, and affecting the health of human beings, thereby causing enormous economic costs.5-8 In fact, the impact of invasive species on biodiversity is rated second only to habitat fragmentation and even greater than pollution.2 The problem of biological invasion is thus globally recognized and threatens the ecological and economic integrity of the invaded area.9,10 However, the impact varies from one part of the world to another depending on the geographic features, diversity of landscapes, and human population density.11,12 Sakai et al.13 pointed out that invasive plants quickly respond to anthropogenic changes and have the ability to undergo genetic changes owing to selection pressure.